The Queen and JK Rowling are the only British women to appear, in 26th and 78th place respectively.

US Secretary of State Hillary Clinton is second, while Brazilian President Dilma Rousseff is third in the list which, although international, is dominated by Americans.

The ninth annual ranking sees the Queen, who at 86 is the oldest on the list, rise 13 places from last year, possibly due to her prominence as she recently celebrated her Diamond Jubilee.

Other formidable females with British links are magazine editor Tina Brown, who was born in the UK but is now an American citizen, and Marjorie Scardino, chief executive of publisher Pearson, who, although from the US, currently resides in London. The pair came in 77th and 86th respectively.

According to Forbes, this year's index represents women who are pioneers in politics, business, media, humanitarian concerns, entertainment and, for the first time, the technology industry.

It also features a number of women who are listed due to their wealth, with all ranked by money, media presence and impact.

The top figures in the entertainment industry are Americans Lady Gaga in 14th place, Beyonce Knowles in 32nd, Jennifer Lopez in 38th and Angelina Jolie in 66th, while Colombian singer and philanthropist Shakira is in 40th position.

Mrs Merkel tops the list for the second year running while US First Lady Michelle Obama, who was number one in 2010, has now dropped down to seventh place.